The structure of a jazz performance is, like that of the New York skyline, a tension of cross-purposes. In jazz at its characteristic best, each player seems to be—and has the sense of being—on his own. Each goes his own way, inventing rhythmic and melodic patterns which, superficially, seem to have as little relevance to one another as the United Nations building does to the Empire State. And yet the outcome is a dazzlingly precise creative unity.